1. Field of the Invention
The invention relates to internal mold release agents useful for the preparation of molded parts by reaction injection molding. More particularly, the invention relates to mold releases prepared by the amidation or esterification of mixtures of montanic acid and carboxylic acids having more than ten carbons, with polyols, alkanolamines, and polyamines
2. Description of Related Art
The preparation of cellular, microcellular, and noncellular molded parts having a closed surface layer made from polyurethane-polyurea elastomers by means of the injection molding technique in closed molds is the subject of numerous technical and patent publications. For example, Federal Republic of Germany published application No. 26 22 951 (U.S. Pat. No. 4,218,543) describes polyurethane systems containing organic polyisocyanates; polyols; reactive aromatic diamines or polyamines which are substituted by alkyl groups in the ortho position of the amino groups; and powerful catalysts for the reaction between the hydroxyl and isocyanate groups. The extremely rapid reaction between these basic components has been claimed to eliminate the need to use release agents to demold the molded parts from polished metal molds In spite of these claims, however, the use of release agents based on wax or silicone as well as of internal release agents such as those cited in Federal Republic of Germany application No. 19 53 637 (U.S. Pat. No. 3,726,952) and Federal Republic of Germany application No. 21 21 670 (GB No. 1,365,215) is widespread.
As illustrative of such release agents, Federal Republic of Germany application No. 19 53 637 discloses salts derived from an organic acid which is aliphatic mono- or polycarboxylic acid having at least 25 aliphatic carbon atoms with a base which may be a primary mono-, di-, or polyamines having two or more carbon atoms, or an amide or ester group-containing amine having at least one primary, secondary, or tertiary amino group. In Federal Republic of Germany application No. 21 21 670, on the other hand, reference is made to a mixture of at least two compounds of the group consisting of amine carboxylic acid salts disclosed in accordance with Federal Republic of Germany application No. 19 53 537; the saturated and unsaturated COOH- and/or OH-group-containing esters of mono- and/or polycarboxylic acids; and polyfunctional alcohols, or natural and/or synthetic oils, fats, or waxes, for use as release agents.
Despite the use of these release agents, in primary aromatic diamine containing formulations used for producing polyurethane-polyurea molded parts by means of injection molding techniques, generally all that can be achieved is a slight improvement in self-release properties. When release agents containing acid groups, in particular carboxylic acid groups, are used, a further disadvantage is that the catalysis of the highly reactive formulation is disrupted, so that molded parts are produced which have insufficient initial green strength.
To avoid this disadvantage, European published application No. 81 701 uses as the polyol component, polyethers containing at least 50 percent primary and/or secondary amino groups. In this way, the use of external release agents is avoided. However, using expensive polyether polyamines not only increases the cost of the resulting molded parts, it also limits their general application because of the resulting change in physical properties.